1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing a centrifugal pump without a shaft. More specifically, the invention relates to a submersible centrifugal pump having multiple impellers, wherein the impellers interconnect and rotate together without the use of a central shaft.
2. Description of the Related Art
Electrical submersible pumps (“ESP”) are used to pump wellbore fluids from the depths of the earth to the surface. A typical ESP has a motor, a seal section, and a pump. The motor rotates a shaft inside the seal section. The seal section shaft is connected to the pump. The ESP pump is typically an impeller pump having multiple stages. Each stage has an impeller and a diffuser. In operation, wellbore fluids enter the first impeller and are accelerated by centrifugal force out of the impeller into the adjacent diffuser. The diffuser reduces the velocity of the wellbore fluid, converts the high velocity to pressure, and directs the fluid into the next impeller. The pressure of the wellbore fluid is increased with each successive stage, until the fluid is discharged from the pump into tubing that carries the fluid to the surface.
A central pump shaft is connected to the seal section shaft. As the motor rotates, it ultimately causes the central pump shaft to rotate. The central pump shaft passes through each impeller. Keys or splines on the shaft engage corresponding slots on each impeller so that the impellers rotate with the shaft. Spacers are frequently required between the impellers so that the impellers are properly spaced to engage the diffusers.
Assembly of the pump can be time consuming and costly. The spacer lengths must be calculated, each of the impellers and spacers must be attached to the central pump shaft, and then the assembled central pump shaft, spacers, and impellers must be installed in the pump housing. It would be advantageous to eliminate the central pump shaft and spacers, thus reducing material costs and assembly time.